1. Flexures for Optics

2. Outline Brief overviews of micro flexures Focus on macro flexures in this tutorial Beam bending Symmetry -> precision Degree of freedom (DOF) Applications

3. Micro Flexures Comb drive Tip-tilt mirrors discrete vs analog

4. Optical MEMS devices Analog tip-tilt mirror Resonant frequency of the comb drive depends on the ions hitting the pads

5. Motivation Need nanometer precision to manipulate light. “Stage” and “driving mechanism”. Sticktion is a problem encountered with screw-type driving mechanisms. Use piezoelectric, capacitive, magnetic, photon,… to drive the “stage”.

6. Precision Mechanics

7. Macro Flexures – 1D

8. Symmetry in 2D In-plane rotation Parasitic motion not di-coupled As soon as the stage moved, Fx developed some “local” y component In-plane rotation minimized Parasitic motion reduced or cancelled Less cross-talk

9. Parallelogram In-plane rotation constrained Parasitic motion reduced As soon as the stage moved, Fx developed some “local” y component In-plane rotation constrained Parasitic motion further reduced or cancelled Less cross-talk

10. Deformation Diagram X/Y forces + X/Y moments

11. 5 DOF – Pentaflex Combination of vertical and horizontal blades X/Y/Z translation + X/Y rotation

12. Highly Symmetric XY Stages Three different anchoring geometries Can be made into XYZ stages by adding the horizontal blades like Pentaflex

13. Diaphragm Flexures Provide out-of-plane (z, ,  ) motions Constrain the other in-plane (x,y,  ) motions (Voice-coil, pressure sensor, flow control, MEMS devices)

14. 6-axis (nano) Flexures  HexFlex

15. 6-axis Flexures - examples

16.  Flexures Only allows  DOF, all others conflict.

17. Tip-tilt Flexures Remove axial misalignment between two parts (shear), but does not remove torque/moment.

18.  flexure -> 5 DOF

19. In-plane 1D Flexure Out-of-plane 1D flexure In-plane 1D flexure Symmetric dual 4-bar linkage eliminates  Y errror

20. Uniform Shaft Loading

21. XYZ Translation Stage Conflict for all  DOF’s

22. Bi-stable Flexure Actuation force causes deflection Open/close a valve at some pressure threshold; on/off Have negative stiffness in the unstable region

23. Non-linear Spring Constant Shape -> deflection -> variable stiffness

24. Piezoelectric Amplifier

25. Physik Instrument Piezoelectric drive + capacitive sensor, feedback loop to actively take out platform vibrations

26. Conclusion Use flexure to avoid sticksion. Use symmetry to cancel/de-couple motions. In-plane vs out-of-plane configurations Flexures for translation, rotation, and any combination of DOF (1-6 DOF). Dynamic range and linearity. Soft flexure -> low resonant frequency, stiff flexure -> high actuation force. References: see FlexureForOptics.doc